1. Field of the Invention
This invention relates generally to ball screw drive arrangements, and more particularly, to an arrangement that provides an indication of failure resulting from the escape of the balls or the diminution in the size of the balls as a result of excessive wear.
2. Description of the Related Art
Primary load path failure is the type of malfunction most desired to be detected in flight controls today. Due to the vital role of ball screws in the safety of a flight, the monitoring of the integrity of the primary load path and the early and accurate detection of failures have became a requirement in modern aircraft.
It is an advantageous characteristic of ball screw drive arrangements at that they are capable of exerting very large loads while achieving high rates of reliability. However, in applications where a failure of a primary drive system might yielded disastrous results, a secondary drive system can be configured to assume the load. In some unknown arrangements, a secondary drive system is coupled axially to the primary load system. It is a problem with such known arrangements that there is no indication provided to the operator that the primary load system has failed. Although rare, a principal mode of failure of the principal drive system is the escape of the recirculating balls. Additionally, there is the possibility that the balls within the system do not escape, but become worn to the point that the primary load system can be deemed to have failed. There is, therefore, a need for an arrangement that provides indication of primary load system failure.
It is, therefore, an object of this invention to provide an arrangement that provides indication of failure of the primary load carrying system of a ball screw drive arrangement.
It is another object of this invention to provide an arrangement that provides indication of the absence of the load bearing balls.
It is also another object of this invention to provide an arrangement that provides indication that a secondary load bearing system has assumed to a load.
It is also an object of this invention to provide a change in the electrical characteristics of an electrical element upon the occurrence of a failure in a primary load bearing system.
It is a further object of this invention to provide a change in the optical characteristics of an optical element upon the occurrence of a failure in a primary load of bearing system.